Prior art attempts to precisely maintain a shaft in a fixed, predetermined position of adjustment when the shaft was subject to rotational and thrust forces have commonly utilized set screw of various configurations to achieve this positioning. In general, these prior art set screws are fitted into a threaded bore in a shaft positioning element and lie perpendicular to a shaft's axis, arranged so that a contact end of the set screw engages a point on the surface of the shaft. This provides the locking force to resist rotational and axial movement of the shaft.
When employed in a machine, this arrangement is often used as an adjustment control to adjust and then maintain the shaft position both axially and in a rotational orientation sense. Other machine elements are also able to be adjusted and locked in this way.
A major disadvantage of the prior art shaft locking assemblies is that, where significant force is required to be generated by the set screw, so as to counteract forces applied to the shaft, the necessary forces are often so great that they cause deformation of the set screw, or cause the contact end of the screw to gouge or form indentations in the shaft body. When an operator was required to make an adjustment to the position of a typical prior art shaft, the set screw was loosened and the shaft was then rotated from its original position to a new or adjusted position. It was then locked in place by engaging the set screw against the shaft.
However, when only a slight rotational adjustment of the shaft was necessary or desired, and when the shaft was deformed or damaged as referred to above, the contact end of the set screw would often engage the indentation previously made in the shaft. When the screw was tightened, it registered with the indentation, causing the shaft to rotate back to its previous position. In other words, the indentation served as a self-centering locating groove unique to a single position.
The operator was therefore required to rotate the shaft well beyond the previously formed indentation, and then tighten the screw against a different portion of the shaft. This in turn could cause additional indentations, eventually preventing the operator from making desirably precise adjustments. This inability to perform the desired adjustments often resulted in machinery operating at less then peak effectiveness; it also sometimes created premature wear and/or damage to the points requiring adjustment.
The same situation occurred when flat spots were created by blunt screw ends.
Another drawback of the prior art shaft locking assemblies was the inability to sequentially lock the shaft against axial movement while still allowing rotational movement of the shaft, then finally locking the shaft against rotational movement. When precise axial positioning and rotational orientation of a shaft utilized as an adjustment or control in a machine is required, it is sometimes desirable to initially to locate the shaft in a predetermined longitudinal position to prevent axial displacement of the shaft while still allowing adjustments to, and subsequent locking of, the rotational positioning of the shaft With prior art set screws, the axial position and rotational orientation of the shaft were often required to be performed simultaneously, making it difficult to precisely fix the shaft in a desired position of multi-axis adjustment.
Additionally, when the contact end of the set screw was deformed from prior use, the contact end of the screw did not always engage the shaft perpendicular to the shaft's axis, frequently causing undesired movement of the shaft either axially or rotationally, also making it difficult or virtually impossible to precisely adjust the position of the shaft. The foregoing problems are not configured to shafts alone, but apply to other machine parts or elements, also.
In accordance with the present invention, some or all of these problems associated with the prior art have been substantially eliminated by providing a new form of adjustment mechanism having several advantages.
It is therefore a principal object of the present invention to provide an improved positioning and locking assembly for shafts or other machine elements.
Another object of the present invention is to provide a shaft locking assembly that fixedly maintains a shaft subject to rotational forces in a desired position without significant deformation of the surface of the shaft body.
Yet another object of the present invention is to provide a shaft locking mechanism wherein the portion to be locked and the set screw end have cooperating contoured surfaces of predetermined form. A further object is to provide a mechanism wherein the axes of the shaft or other machine part and the set screw are arranged in a predetermined relation.
Another object is to provide an adjustment mechanism whereby, in use, a portion of the shaft may be put in tension initially to prevent axial movement of the shaft, while still allowing some rotation of the shaft for adjustment purposes before final locking.
Still another object of the present invention is to provide a shaft locking mechanism utilizing cooperating contact surfaces on a shaft and a screw end, with the shaft and the screw having their axes generally perpendicular to each other but slightly offset from each other.
A still further object is to provide an adjustment mechanism wherein set screw movement sequentially prevents axial movement of the shaft and then rotational movement of the shaft as engagement between the contoured surfaces increases.
Yet another object of the present invention is to provide a precisely adjustable linear motion control for pushing closures onto containers that pass therebeneath, with such control utilizing a shaft locking mechanism having intersecting contoured surfaces, permitting the fine adjustments and retention forces necessary to accommodate various size closures and containers.
A further object of the invention is to provide a adjustment mechanism wherein a shaft element includes a contoured groove having a locus of maximum depth groove centerline lying in a plane perpendicular to the part axis, with the mechanism further including a set screw arranged so that its axis is perpendicular to but offset from the part axis but lies in the plane of the groove centerline.
Yet another object of the invention is to provide an arrangement of moveable machine parts, including a part with a positioning groove and a set screw wherein restriction against axial movement may be provided during the tightening sequence without restricting the availability of locational adjustment, wherein final locking is achieved by a wide area surface contact or interference accompanied by slight deformation of the cooperating parts within their limits of elasticity.
Other objects and advantages of the present invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.
The foregoing and other objects and advantages of the invention are achieved in practice by providing a locking device for precisely maintaining axial and rotational position of a machine part, with the mechanism including a shaft positioning element having an opening lying along a first axis for receiving a rotatable part, a rotatable and axially moveable part positioned within the opening and including a groove having its centerline or locus of maximum depth lying perpendicular to the machine part rotational axis, with the shaft positioning element further including a threaded set screw arranged coplanar with the groove plane and perpendicular to but offset from the shaft axis with a set screw having a contoured end face moveable into cooperating engagement with a portion of the groove surface.
For a complete understanding of the present invention reference is now be made to the embodiment illustrated in greater detail in the accompanying drawings and described below by way of example. It should be understood that this invention is not limited to the particular embodiments illustrated herein but is defined by the appended claims.